The degradation of cellular molecules is a normal process that can go awry. Defects in the degradation of various cell macromolecules cause disease and are usually the result of mutations in specific enzymes. Two key enzymes in the degradation of cellular carbohydrates are alpha-N-acetylgalactosaminidase and alpha-galactosidase. Mutations in these enymes cause forms of Shindler and Fabry disease, repectively. We are determining the structures of these two enymes in order to map the locations of the mutations that give rise to the diseases and to describe the catalytic mechanisms by which the enzymes perform their normal function of carbohydrate degradation.